Fig. 4: Interaction with ACE2 enhances S processing.

a Schematic representation of the SARS-CoV-2 S protein: FL (purple), S2 (yellow), S2′ (orange), and sequence alignments of the SCoV-2 and RaTG13 S1/S2 and S2′ cleavage sites. b Exemplary immunoblots of whole cells lysates (WCLs) and supernatants of HEK293T cells expressing SCoV-2 S, RaTG13 S, or the indicated mutant that were infected with VSVΔG-GFP in the absence (left) or the presence of a vector expressing human ACE2 (right). Blots were stained with anti-SCoV-2 S, anti-GAPDH, anti-ACE2, and anti-VSV-M. and quantified for Spike FL, S2, and S2′ expression. Bars represent the mean of three independent experiments (±SEM). c Automated quantification of GFP fluorescence of A549 ACE2 cells infected with VSVΔG-GFP pseudotyped with indicated SCoV-2 or RaTG13 S in the absence of ACE2. The cells were pre-treated (30 min) with 20 µM of E64-d or Camostat in the highest concentration and diluted in a 1:2 titrational row. Lines represent the mean of three independent experiments (±SEM).